I have set up and supported remote sites and home based telecommuting. Listen to my advice, listen very carefully and save your sanity.
If your organization is large enough then it is likely that you will have a few older desktop PCs that have been or are due for replacement during an upgrade cycle. PCs that are inadequate for Microsoft XP and Office2003 are more than powerful enough for many current versions of Linux, especially for the role of server. Also second hand PCs with the required specifications are very cheaply acquired.
1) Find an older PC, at least a PII 300 with 256 MB memory, to set up as a headless ( no display or keyboard ) server and firewall. A simple web based interface ( or even an external hardware push button ) can be used by the local users to start/stop the server and internet connection. All other maintenance should be handled remotely via ssh, webmin and VNC.
2) Install a second NIC or connect the modem directly to the server. Connection to the Internet should be through the server and connection to the Office should be through a VPN on the server. Use a dynamic IP service for each site so you can remotely log on to the local server via ssh.
3) Install a new IDE hard drive in a 3.5" removable rack and tray. The drive should be than big enough for the operating system (Linux of course) and copies of some of the local desktop partitions. A telecommuter can shut down the server and bring in the drive during the day to resync and repair.
4) Install a DHCP demon on the local server to allocate local IP addresses, DNS and gateway settings. If the desktops are network boot capable then install TFTP to remotely boot and use Knoppix via PXE and the network. If the desktop OS is constantly crashing, or is infected by malware, the user can select PXE/network boot via the BIOS, and boot into Knoppix. The user can then be instructed over the phone to enable the ssh server to allow remote scan,repair and reimaging of the desktop partitions. The user can use the Knoppix desktop to continue working with full access to files while the the remote administrator fixes/reimages the drive in the background.( Consider hiring someone who knows how to customise Knoppix or another live Linux system for your setup )
5) Partition the desktops with as small as required C: partition ( or in the case of Linux the root partition ) for software. When software is install, use dd and netcat via live Knoppix to copy/clone a snapshot of the partition to the server. You can allocate the remaining free space as a persistent partition where documents are stored.
6) Install and enable remote VNC service on all the platforms, but only allow incoming connections from the local server ( which is redirected over a SSH tunnel ).
7) For local backup, create share directories on the desktop accessible by the server. On the local server create loopback encrypted file systems, unmount and copy the images to the desktops shares in chunks, using redundancy if enough space is available on the desktops. Checksum ( MD5 is enough ) each piece.
8) If the network load to the Office is taking up all the available internet bandwidth or the connection is just too slow then install proxy servers on the local server. You can also consider using a distributed filesystem ( OpenAFS is still the best ) with access to the local users via a SAMBA share.
9) If phone charges are eating into the budget, and the internet connection is good enough, then install Asterisk on the local server ( upgrade the server to a Celeron 800Mhz or better ) and PCI cards with enough FXS ports for each local user. Don't bother with software based phones/headsets. The phone will work when the desktop does not.
10) Set up a Linux server at the Office that operates as a thin client application server. Allow remote access though both FreeNX and VNC. Create login accounts and logins that operate as virtual meeting rooms, with multiple users logging in via VNC. Use VNCserver with a screen size of around 1000x600, that will operate via a VNC viewer on any 1024x768 desktop. Use phone based conference calling for voice -- it's a lot less hassle for the users
11) Add the usual list of cross platform applications: Firefox, Thunderbird, Gaim, and even OpenOffice etc.
The return on investment from the reduction in desktop downtime will quickly outweigh any initial outlay for any new hard drives and possibly FXS cards.